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Immune System
C) Body’s defense against germs
1) Define immunity- your body’s resistance to germs and the
harmful substances they produce
2) How do these five things fight off germs from entering your body?
FIRST LINE OF DEFENSE
-Tears – Wash germs from your eyes
-Skin – if the skin is unbroken, you are protected. Germs
enter when you are cut, burned or scraped
-Mucous Membrane – in your nose, mouth and throat. Secrete
mucus that traps germs
-Saliva – washes germs from your mouth and cleans your
teeth.
-Gastric Juices – produced in your stomach, they destroy
germs
MAIN LINE OF DEFENSE
3) What role does a phagocyte play in your immune system? What is
otherwise known as? Engulf and destroy germs once they do enter
your body (phagocytosis)
1) What does interferon do? A substance that is released by the
body when a germ is present and stops the virus from
reproducing and infecting other cells
2) When you are ill, you body raises it’s core temperature. Why? It is
killing germs that cannot survive higher body
temperatures
SPECIFIC IMMUNITY – if the germs do survive the general immune
reaction (phagocytosis), your lymphatic system takes over
D) Lymphatic System – a secondary circulatory system of vessels
and nodes that carry lymph. It helps maintain the balance of fluids in
the body that help fight germs.
1)
2)
Lymph nodes – small lumps of tissue located
throughout the system that filters to keep germs from
invading body tissues. When a germ infects the area,
your lymph nodes become swollen because they are
in action.
Lymphocytes – Special white blood cells in lymph
a. B-Cells – fight germs
b. T-Cells attach germs and stimulate B-Cells to work
HOW THE IMMUNE SYSTEM RESPONDS TO VIRUSES
 Virus enters body – makes it past the first and main line of
defense
 T –Cells identify the virus and multiply and activate B-cells
 B-Cells multiply and produce antibodies (proteins that
attach to germs and prevent them from harming the body)
or stuns them
 Special T-Cells destroy the virus
 Memory B-cells and T-cells store the virus or germ to
memory in case of re-entry
E) Vaccine – Dead or weakened germs that are injected into the
body to cause the immune system to produce antibodies against
it.